Acid resisting alloy



May 10, 1938. R. B. MCCAULY 2,117,191

AC ID RESISTING ALLOY Filed Jan. 17, 1930 @/MWVWI Patented ay i, i938 ACID RESHS'llING ALLUY Roy B. McCauley, Chicago Heights, 1li. Application January 17, 1930, Serial No. 421,535

metal into a' phosphide, either Wholly or to such an extent as will give it a desired degree of acid resistance, and consists in various applications of this principle, several of which arey hereinafter specifically described.

According to one application of thezinvention, iron, which is a very desirable metal for many uses because of its cheapness, is rendered capable of use for the purposes of the present invention, notwithstanding it hasheretofore been generally recognized that the addition of phosphorus in substantial proportions renders it too brittle for use for mechanical purposes; a subordinate feature of the present invention which renders it applicable for use in acid-proofing iron consisting in adding to the alloy a metal or metals having the capacity of neutralizing the brittleness (hereinafter called disembrittling) of the iron which would ordinarily result from the conversion of the iron into phosphde.

Metals which are preferably used in lending this physical characteristic to iron phosphide are those which have in themselves the capacity of alloying with the phosphorus and becoming phosphides, and thereby rendering this element, as well as the iron phosphide, immune to acid or other oxidizing inuences to a desirable degree. The metals which have the capacity of reducing brittleness of iron phosphide to the extent of making it available for mechanical purposes and at the same time becoming, themselves, phosphides to a beneficial degree in the alloy, are well illustrated by the metals copper and chromium. These two disembrittling agencies are each found to have certain characteristics which render them preferable under certain circumstances; for instance, the copper will be a preferable ingredient to use when the disembrittled iron phosphide is to be used for a purpose that subjects it to the influence of halogen acids or acids of the chlorine group or type, and sulphates, whereas the chromium would be a preferable disembrittling agent for use where the ultimate article made from the iron phosphide will encounter oxidizing influences such as those resulting from contact with nitric acid, acetic acid. and the like. An important advantage of the present invention, in addition to those already mentioned is that the phosphides herein referred to are much more In the accompanying drawing-- Figures 1, 2, and 3 show, respectively, an industrial vat, a section of a pipe or conduit, and a pump as illustrative of containers made from an alloy embodying the subject-matter of the present invention.

The approximate limits of the proportions of the alloying ingredients will be as follows:

With iron from 95 to 75% and phosphorus from 5 to 25%, iron phosphide would be produced which would be resistant, even with the 5% phosphorus, to an appreciably useful degree to the influences of acids and alkalis, and to an exceedingly high degree if the proportion of phosphorus ran as high as 25%. But such an alloy, and particularly with the higher proportions of phosphorus, would be exceedingly brittle, so that it could not be used for many mechanical purposes. Accordingly, if one of the disembrittling agents typified by the copper or chromium hereinmentioned is added, the proportion of copper decreasing as the proportion of phosphorus increases, and the proportion of iron increasing directly as the proportions of phosphorus but indirectly as the proportions of theV copper, the alloy will have sufcient` inherent strength to serve for the production of mechanical articles generally, and particularly those which require to be highly resistant to acid and other` oxidizing influences. The disembrittling agents, copper or chromium, may be added in proportions of from 80% down to 5% with the iron increasing from to 74% and with the phosphorus increasing from 5 to 21%. `In adding a disembrittling agent, as explained, this agent itself is converted into a phosphide to an appreciably beneficial degree, and to an increasing degree as the proportion of copper decreases and the phosphorus increases.

If chromium be used, as the disembrittling agent, better results will be obtained in resisting acids, such as nitric acid andy acetic acid than if .copper were used, although, perhaps without obtaining quite the high degree of disembrittling.

Among the more specic formulas which have been found to produce good results, are the following: An alloy consisting of iron 41.65%. phosphorus 15.95%, and copper 41.74%, and with the impurities silicon, manganese and carbon existing at not greater than 0.13, 0.23, and 0.30%, respectively when' subjected to 3% suiphuric acid at 212 F. for three hours', Vwhen subjected to hydrochloride acid at 212 shows a solubility of 0.055%; 

